Related art has been disclosed (for example, see Japanese Patent Application Laid-Open No. 11-254992) that aims to inhibit rollover of a vehicle by reducing a lateral acceleration thereof. In the case that there is an indication that rollover may occur, namely, a rollover tendency, when a vehicle is turning sharply, the lateral acceleration is reduced by causing vehicle speed to be slowed by executing automatic reduction of engine output and applying a brake.
With this related art, it is determined whether the vehicle has a rollover tendency based on whether or not (1) a wheel speed of a drive wheel that is positioned at the inside of a turn direction of the vehicle is greater than a predetermined value, or (2) an acceleration of this drive wheel is greater than a predetermined value. When it is determined that the vehicle has the rollover tendency, namely, that the wheel speed of the drive wheel at the inside of the turn direction, or the acceleration thereof, exceeds the predetermined value, engine output is reduced and the brake is applied.
However, with this related art, reduction of engine output and application of the brake is not executed unless the wheel speed of the drive wheel at the inside of the turn direction, or the acceleration thereof, exceeds the predetermined value. Accordingly, reduction of engine output and application of the brake is executed suddenly at the point when the wheel speed or acceleration thereof has increased enough to exceed the threshold value. Thus, control of vehicle speed change and lateral acceleration change is started abruptly, which causes vehicle posture to change substantially, thus having a detrimental impact on driving feeling.